Tree Facts: Winter burn

FFAGENTS

Many evergreens throughout northwestern South Dakota have winter burn injury this spring. It is showing up as reddish-brown dead foliage and was caused by cold winds which dried out the needles of evergreens last winter. Desiccation occurs when the ground contains inadequate moisture due to drought, frozen ground or whenever else a plant is unable to access moisture in the soil. Windy sites are obviously more prone to this type of damage than protected locations. Plant roots cannot uptake water from frozen soil to replace the losses experienced in the leaves. The longer these conditions exist, the more moisture is lost and death of leaf tissue results. Early fall or late spring freezes can kill evergreen foliage when it is not adequately hardened off. If the damage is severe, some or all of the buds also may die.

Usually the north and west sides of trees experience the worst damage from the prevailing winds. Other conditions that can contribute to a trees susceptibility to winter burn are if it has been planted improperly, stressed by insects, diseases, other environmental factors, fertilized at an improper time or have poor winter hardiness. Normally only foliage is killed and buds and branches usually are unaffected. Foliage that both early fall freezes and winter desiccation killed often remains green as long as temperatures are cold. Damaged needles then turn brown when temperatures rise. If the buds were not killed, new foliage emerges the spring or early summer. Assessment of total injury should be made only after new growth has occurred. Winter injury often is an aesthetic problem in evergreens but does kill trees occasionally.

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There some actions that can be taken to reduce the incidence and severity of winter burn in the future. Plant only drought tolerant trees and shrubs. Some examples of drought tolerant evergreen species that are less prone get winter burn are as follows: Rocky Mountain Juniper, Eastern Red Cedar, Lodgpole Pine, Ponderosa Pine and Mugo Pine. If it is a dry year water trees adequately during the summer and fall. There are products available which can reduce this injury when used properly. They are in a group of chemicals known as anti-desiccants or anti-transpirants and sold under trade names such as Wilt-Pruf, Nu-Film, VaporGuard, and Stressguard. The products used in the winter create a barrier over the pores or stomates in the leaf, which allow the plant to breathe but reduce water loss through transpiration.

My source for this news release was North Dakota State University Extension Service. If you would like more information about Winter Burn, call Bob Drown at the Conservation Office at 605-244-5222, Extension 4.